The Piezometric Head

The sum of pressure head - p / γ - and elevation head - h - is called the piezometric head. The piezometric head in a flow can be measured through an flat opening parallel to the flow.

The Energy Line

The Energy Line is a line that represent the total head available to the fluid and can be expressed as:

EL = H = p / γ + v2 / 2 g + h = constant along a streamline (3)

where

EL = Energy Line (m)

For a fluid flow without any losses due to friction (major losses) or components (minor losses) - the energy line would be at a constant level. In a practical world the energy line decreases along the flow due to losses.

A turbine in the flow reduces the energy line and a pump or fan in the line increases the energy line.

The Hydraulic Grade Line

The Hydraulic Grade Line is a line representing the total head available to the fluid - minus the velocity head and can be expressed as:

HGL = p / γ + h (4)

where

HGL = Hydraulic Grade Line (m)

The hydraulic grade line lies one velocity head below the the energy line.

Related Topics

Fluid Mechanics
- The study of fluids - liquids and gases. Involves velocity, pressure, density and temperature as functions of space and time